With the advancement of science and technology, fluid control devices are widely used in many sectors such as pharmaceutical industries, computer techniques, printing industries or energy industries. Moreover, the fluid control devices are developed toward elaboration and miniaturization. The fluid control devices are important components that are used in for example micro pumps, micro atomizers, printheads or industrial printers for transporting fluid. Therefore, it is important to provide an improved structure of the fluid control device.
For example, in the pharmaceutical industries, pneumatic devices or pneumatic machines use motors or pressure valves to transfer gases. However, due to the volume limitations of the motors and the pressure valves, the pneumatic devices or the pneumatic machines are bulky in volume. In other words, the conventional pneumatic device fails to meet the miniaturization requirement and is not portable. Moreover, during operations of the motor or the pressure valve, annoying noise is readily generated. That is, the conventional pneumatic device is neither friendly nor comfortable to the user.
FIG. 6 is a schematic cross-sectional view illustrating a conventional miniature fluid control device. As shown in FIG. 6, the conventional miniature fluid control device 1′ comprises a gas collecting plate 11′, a piezoelectric actuator 12′, an adhesive layer 13′ and a base 14′. The gas collecting plate 11′, the piezoelectric actuator 12′, the adhesive layer 13′ and the base 14′ are stacked on each other sequentially. The base 14′ comprises a gas inlet plate 141′ and a resonance plate 142′. The gas inlet plate 141′ comprises at least one inlet 143′, each of which is in communication with a central cavity 145′ through a convergence channel 144′. The resonance plate 142′ has a central aperture 146′ corresponding to the central cavity 145′. The piezoelectric actuator 12′ comprises a suspension plate 121′, an outer frame 122′, at least one bracket 123′ and a piezoelectric ceramic plate 124′. A gap h0′ is formed between the resonance plate 142′ and the outer frame 122′ of the piezoelectric actuator 12′. The adhesive layer 13′ is filled in the gap h0′. Consequently, a compressible chamber 10′ is defined between the resonance plate 142′ and the piezoelectric actuator 12′. The gas collecting plate 11′ has a first perforation 111′. Moreover, the piezoelectric actuator 12′ is covered by the gas collecting plate 11′. As the piezoelectric actuator 12′ is actuated by an applied voltage, the suspension plate 121′ of the piezoelectric actuator 12′ is vibrated along a vertical direction in a reciprocating manner. Consequently, an external fluid is introduced into the inlet 143′, guided to the central cavity 145′ through the convergence channel 144′, and transferred to a compressible chamber 10′. As the volume of the compressible chamber 10′ shrinks, the fluid exits through the first perforation 111′ of the gas collecting plate 11′. Consequently, a specified pressure is generated. Moreover, the suspension plate 121′, the outer frame 122′ and the bracket 123′ are integrally formed with each other and produced by using a metal plate. An etching process including multiple steps is applied to the metal plate to make the top surface of the outer frame 122′ at a level higher than the suspension plate 121′. That is, there is a height difference between the outer frame 122′ and the suspension plate 121′. The adhesive layer 13′ is made by coating an adhesive on the top surface of the outer frame 122′ to fill in the gap h0′, therefore forming and maintaining a required depth h′ of the compressible chamber 10′ between the resonance plate 142′ and the suspension plate 121′, which can reduce the contact interference of the resonance plate 142′ and the suspension plate 121.
However, the conventional miniature fluid control device still has some drawbacks. The required depth h′ of the compressible chamber 10′ consists of two parts: one is the height difference between the outer frame 122′ and the suspension plate 121′; and another is the thickness of the adhesive layer 13′, which is as tall as the gap h0′. Since the outer frame 122′ is made of a metallic material, the outer frame 122′ has specific degree of rigidity. Generally, the thickness of the adhesive layer 13′ is only half of the height difference between the outer frame 122′ and the suspension plate 121′, such thickness is insufficient for exerting proper cushion effect to the whole structure of the compressible chamber 10′. Under this circumstance, the rigidity of the overall structure is too strong that the suspension plate 121′ is unable to effectively absorb interference vibration energy during the vertical vibration of the piezoelectric actuator 12′. In other words, the conventional miniature fluid control device 1′ loses unnecessarily energy and generates undesired noise, and the noise problem may result in the defectiveness of the products.
Therefore, there is a need of providing a miniature fluid control device with small, miniature, silent, portable and comfortable benefits in order to eliminate the above drawbacks.